JPH066484B2 - Method for producing titanium carbide powder - Google Patents

Description

Description: FIELD OF THE INVENTION This invention relates generally to the production of titanium carbide (TiC) powder, and more particularly to high purity T in the submicron range.
The present invention relates to a method for producing iC powder.

<Prior Art> Ceramics and ceramic composites are attracting attention as structural materials used in high temperature environments, particularly in environments where erosion and corrosion conditions exist. For example, several types of ceramics and ceramic composites have been found to be satisfactory structural materials for components used in hot gas turbines and heat engines. Also, parts used in coal conversion facilities can be effectively manufactured from ceramics and ceramic composites.

TiC powder is a refractory material useful for manufacturing cutting tools, grinding wheels, etc., and as described above, aluminum oxide, silicon nitride, carbon carbide is used for manufacturing structural materials used in high temperature erosive and corrosive environments. It can be used in combination with other ceramic systems such as silicon.

Currently, TiC powder is carbon powder at a temperature of about 1700-2100 ° C,
In particular, it is mainly produced by reducing titanium dioxide with carbon black. This TiC powder is produced in a relatively wide range of particle sizes of 1 micron and above due to the individual bonding and particle size growth of the particles during sintering during the reduction reaction. In addition, undesired inhomogeneities are often found in the powder due to the diffusion gradient created during the reduction reaction.

<Problems to be Solved by the Invention> Therefore, the present invention has been made for the purpose of providing a method for synthesizing a high-purity TiC powder having a submicron particle size in which particles are individually separated.

<Means for Solving Problems> The production of TiC powder according to the present invention includes a step of producing a liquid organotitanate or a mixture of an organotitanate solution and a carbon precursor polymer-containing solution.
At this time, the organotitanate and the carbon precursor have substantially stoichiometric concentrations of titanium and carbon, and the organotitanate causes a crosslinking reaction with the polymer to form a gel. The gel is subsequently heated to dry the gel, expel volatile components from the gel and thermally decompose the polymer to liberate carbon. The remaining components in the gel, titanium and carbon, are then heated to a sufficient temperature to convert the titanium and carbon to TiC powder.

The use of cross-linking organotitanates for the production of TiC powders is extremely effective. This is because the titanium in the organotitanate and the carbon in the polymer are mixed at the molecular level to cause the formation of a TiC powder having a stoichiometric composition. In addition, the resulting powder exhibits high purity (99.99% and above) and has little or no heterogeneity due to the molecular level mixing of titanium and carbon provided by the components of the process of this invention.

Other objects of the present invention will be apparent from the following description.

As mentioned above, the present invention provides a method for preparing high purity TiC powder having a particle size in the submicron range. This method uses a high purity solution to formulate and mix the titanium and carbon precursors. Liquid organotitanate or an organotitanate solution is mixed with the polymer solution. The amounts of both are substantially stoichiometric with respect to the titanium and carbon in the organotitanate and the polymer. The organotitanate is the crosslinker for the carbon precursor polymer selected for use in this invention. The organotitanate and polymer formed a gelatinous precipitate, indicating that a crosslinking reaction had taken place. This cross-linking reaction ensures a molecular mixing of titanium and carbon, immobilizes the titanium and prevents subsequent separation of the titanium during the drying and pyrolysis of the cross-linked polymer. . As described below,
In some cases, heating is required to mix the organotitanate with the carbon precursor polymer, which allows the cross-linking reaction to occur to form a gelatinous precipitate. Normally, this heating is performed at a temperature of about 80 to 100 ° C for about 1 to 24
You just have to go on time.

By subjecting this gelatinous precipitate to a drying process at a relatively low temperature,
Easily volatile liquids are removed from this mixture. This drying causes precipitation to occur at temperatures in the range of about 25-100 ° C for about 1-24.
It can be achieved by heating for a time. In some cases, as described below, excess liquid may be included in the gel. Such excess liquid can be easily removed by decantation or other method prior to the drying step. After completion of the drying process, the gel is heated in an inert atmosphere such as argon to a temperature in the range of about 600 to 800 ° C to pyrolyze the polymer to produce free carbon, and at the same time volatility other than titanium and carbon. Remove components from gel. This temperature is usually maintained for about 10-120 minutes to effectively effect thermal decomposition and ensure removal of substantially all volatiles in the gel.

The components of the gel thus dried and freed from volatile components,
That is, cross-linked titanium and carbon, about 1200 ~ 1600 ℃,
The titanium and carbon are reacted by heating in an inert atmosphere such as argon for about 1-2 hours to produce high purity TiC powder. The TiC powder thus produced has a particle size of less than 1 micron.

Liquid organotitanates useful in this invention include:
Tetraisopropyl titanate, titanium lactate chelate,
Tetrabutyl titanate, acetylacetonate chelates, triethanolamine chelates, and similar allyl titanates and titanium chelates such as E. I. D
u Pont de Nemours & Co. (Wilmington, Delaware, USA) and the like, which are commercially available under the trade names such as "TYZOR". The organotitanates exemplified herein are potential crosslinkers for carbon precursor polymers that ensure the desired molecular level mixing of titanium and carbon. Further, this cross-linking makes titanium immobile and prevents the separation of titanium in the process of drying and thermal decomposition of the volatile substances of the cross-linked polymer.
The organotitanates described above are preferred over other organotitanates such as isopropyltri (Nethylamino-ethylamino) titanate or isopropyltri (2-aminobenzoyl) titanate. This is because the preferred organotitanates have a higher concentration of titanium, which leads to the efficient production of TiC, and are more desirable than organotitanates containing a low concentration of titanium. However, organotitanates with a relatively low titanium concentration can also be used to produce TiC according to the invention. In that case, the reaction vessel containing the gelatinous precipitate formed also contained a significant amount of liquid, but this solution can be easily removed from the reaction vessel by decanting prior to drying.

The carbon precursor polymer used in this invention is a hydroxyl group,
Having active hydrogens on amino, amido, carboxyl or thio groups, including polymers such as polyvinyl alcohol, cellulose derivatives, phenols, polyesters, polyvinyl acetates, epoxy resins and similar polymeric materials I'm out. The polymer should be chosen so that it can provide a significant proportion of free carbon to convert titanium to TiC. The polymer is contacted with a relatively volatile solvent so that it is sufficiently liquefied so that it can be well mixed with the organotitanate. Such solvents include alcohols, water, esters, hydrocarbons, halogenated hydrocarbons and mixtures thereof.

<Example> Hereinafter, the present invention will be further described with reference to an example in which organotitanates and carbon precursor polymers are converted into TiC powder in submicron units.

Example 1 Tetraisopropyl titanate (trade name "TYZOR
TPT ", E.I. I. Du Pont de Nemours & C
o. 25 g and phenolic resin (trade name "Durez 316")
49 ", Occidetnal Chem. Co. (Tonowanda, NY) 9.7 g of a 25 ml absolute ethanol solution was prepared and stirred. A gelatinous precipitate formed during stirring. This indicates that a crosslinking reaction between the organotitanate and the polymer had taken place.
The gel was dried at 60 ° C. for 16 hours, then heated at 800 ° C. for 10 minutes under an argon atmosphere to drive off volatile substances and carbonize the polymer. Next, this gel was heated under an argon atmosphere at 1400 ° C. and 1600 ° C. for 1 hour to react titanium with carbon to obtain fine TiC powder. As a result of measuring the surface area, the particle size of this powder was in the submicron unit. X-ray diffraction also showed that this powder was pure TiC in all cases.

Example 2 Titanium lactate chelate (trade name “TYZORLA”, E.I.
I. Du Pont de Nemours & Co. Made, CAS
No.65104-06-5) and an aqueous solution of 61.2 g of methylcellulose (trade name "Metho-cel" D, ow Chemical Co. (Midland, Mich., USA)) (61.2 g) and stirred for 5 minutes. did. No reaction was observed at room temperature, but when the mixture was heated at 85 ° C. for 16 hours, an irreversible gel was formed in the container. From this, it can be seen that a crosslinking reaction occurred between the organotitanate and the methyl cellulose. The gel was subsequently dried, the temperature was gradually raised to 800 ° C. under an argon atmosphere, and the temperature was kept at 800 ° C. for 10 minutes to thermally decompose the polymer. The obtained non-volatile solid was placed in argon at 1400 ° C, 1
The reaction was carried out for a time to produce a fine TiC powder.

<Effect of the Invention> It will be understood that the TiC synthesizing method of the present invention has some advantages as compared with the conventional method. An important point of submicron powder formation according to this invention is the cross-linking reaction between the organotitanates and polymers which results in the molecular mixing of titanium and carbon. An important advantage of the present invention is also that it is used to react titanium with crosslinked carbon to produce TiC at 1400-1600 ° C.
That is, the maximum temperature is considerably lower than that of the conventional method, which is advantageous in terms of energy efficiency and cost. In the conventional method, a carburizing temperature of about 1700 to 2000 ° C was required.

This invention aims at synthesizing TiC powder which is used by being dispersed in other ceramic-based matrix such as silicon carbide and aluminum oxide. It will be appreciated that it may be added into the solution of precursor and organotitanate. In this case,
In addition to the cross-linked titanium and polymer, the particle size matrix material will also be included in the gel mixture, and when heated to produce TiC, a fine TiC coating is formed on the surface of the ceramic matrix particles. This fine T
The iC-coated powder can be compacted into a suitable shape by sintering or hot pressing well known in the powder metallurgy art.

Claims (1)

[Claims] 1. An organotitanate by mixing a liquid organotitanate or organotitanate solution and a carbon precursor polymer solution in proportions such that the amounts are substantially stoichiometric for titanium and carbon. The step of forming a gel by causing a cross-linking reaction with the carbon precursor polymer in the above, and heating the gel to dry the gel, expelling volatile components from the gel, and thermally decomposing the polymer to produce free carbon. And then heating the residual components of this gel at about 1400-1600 ° C. for about 1-2 hours to convert titanium and carbon to submicron titanium carbide powder with a purity of 99.99% or more. A method for producing a titanium carbide powder, which is characterized.